How do you get hard water stains out of a toilet?

I need help with that as well and my toilet is new!! Go figure...

You can get a pumice stone meant for this at Home Depot. It does get the toughest mineral buildup off. Over many uses it would dull the finish of the porcelain and potentially cause more buildup (because it would be less "slippery,") so I'd recommend doing it as an initial removal, then prevent additional buildup by using those Clorox tabs that you leave in the bowl, and more frequent cleaning with a normal toilet brush to prevent buildup. This worked for me... my toilets were so bad with mineral buildup I thought I'd have to replace them!

have you tried cleaning vinagar?

I heard you pour a can of coke in and let it sit for a while

https://www.thespruce.com/hard-water-stains-in-the-toilet-2719033

Try some bleach, make the water line past the stain, let sit. Next, use a commercial toilet cleaner, Lysol, Mr. Clean, etc. If that doesn't work use peroxide, the same method.